import { describe, test, expect } from "bun:test";
import {
  fetchAuthStatus,
  login,
  logout,
  register,
  validatePassword,
  validateUsername,
  type FetchLike,
} from "../src/lib/authClient";

// The auth client is framework-free with an injectable fetch, so we can test
// validation, the request contract, and the fail-silent /me behaviour without
// a DOM or a running server (the M4 backend is exercised separately).

function jsonResponse(status: number, body: unknown): Response {
  return new Response(JSON.stringify(body), {
    status,
    headers: { "Content-Type": "application/json" },
  });
}

/** Mock fetch returning a fixed response and recording the call. */
function mockFetch(response: Response | Error): {
  fetch: FetchLike;
  calls: { input: string; init?: RequestInit }[];
} {
  const calls: { input: string; init?: RequestInit }[] = [];
  const fetch: FetchLike = (input, init) => {
    calls.push({ input, init });
    return response instanceof Error
      ? Promise.reject(response)
      : Promise.resolve(response);
  };
  return { fetch, calls };
}

const USER = { id: 1, username: "alice" };

describe("validateUsername", () => {
  test("accepts the allowed charset within 3–32 chars", () => {
    expect(validateUsername("abc")).toBeNull(); // lower bound
    expect(validateUsername("a".repeat(32))).toBeNull(); // upper bound
    expect(validateUsername("User_1.name-x")).toBeNull();
  });

  test("rejects usernames that are too short or too long", () => {
    expect(validateUsername("")).not.toBeNull();
    expect(validateUsername("ab")).not.toBeNull();
    expect(validateUsername("a".repeat(33))).not.toBeNull();
  });

  test("rejects characters outside [a-zA-Z0-9_.-]", () => {
    expect(validateUsername("has space")).not.toBeNull();
    expect(validateUsername("email@host")).not.toBeNull();
    expect(validateUsername("émile")).not.toBeNull();
  });
});

describe("validatePassword", () => {
  test("requires at least 8 characters", () => {
    expect(validatePassword("1234567")).not.toBeNull();
    expect(validatePassword("12345678")).toBeNull();
  });
});

describe("fetchAuthStatus (fail-silent /me)", () => {
  test("returns the user on 200", async () => {
    const { fetch, calls } = mockFetch(jsonResponse(200, { user: USER }));
    expect(await fetchAuthStatus(fetch)).toEqual({ enabled: true, user: USER });
    // The cookie is HttpOnly — it must ride along via same-origin credentials.
    expect(calls[0]?.input).toBe("api/auth/me");
    expect(calls[0]?.init?.credentials).toBe("same-origin");
  });

  test("resolves to anonymous (null user) on 401", async () => {
    const { fetch } = mockFetch(jsonResponse(401, { error: "unauthorized" }));
    expect(await fetchAuthStatus(fetch)).toEqual({ enabled: true, user: null });
  });

  test("resolves to disabled on 404 (AUTH_ENABLED=false, D-015)", async () => {
    const { fetch } = mockFetch(jsonResponse(404, { error: "Not Found" }));
    expect(await fetchAuthStatus(fetch)).toEqual({ enabled: false, user: null });
  });

  test("resolves to disabled on network failure (offline-first)", async () => {
    // /api/* is network-only in the service worker, so offline /me rejects.
    // That must NOT throw or surface an error — the auth UI just stays
    // hidden (signing in is impossible without the server anyway).
    const { fetch } = mockFetch(new TypeError("Failed to fetch"));
    expect(await fetchAuthStatus(fetch)).toEqual({ enabled: false, user: null });
  });

  test("resolves to anonymous on a malformed body", async () => {
    const { fetch } = mockFetch(
      new Response("<html>proxy error</html>", { status: 200 }),
    );
    expect(await fetchAuthStatus(fetch)).toEqual({ enabled: true, user: null });
  });
});

describe("login", () => {
  test("POSTs JSON credentials and returns the user on 200", async () => {
    const { fetch, calls } = mockFetch(jsonResponse(200, { user: USER }));
    expect(await login("alice", "hunter22", fetch)).toEqual(USER);

    const call = calls[0];
    expect(call?.input).toBe("api/auth/login");
    expect(call?.init?.method).toBe("POST");
    expect(call?.init?.credentials).toBe("same-origin");
    expect(
      (call?.init?.headers as Record<string, string>)["Content-Type"],
    ).toBe("application/json");
    expect(JSON.parse(call?.init?.body as string)).toEqual({
      username: "alice",
      password: "hunter22",
    });
  });

  test("surfaces the server's error message on 401", async () => {
    const { fetch } = mockFetch(
      jsonResponse(401, { error: "invalid credentials" }),
    );
    expect(login("alice", "wrong-pass", fetch)).rejects.toThrow(
      "invalid credentials",
    );
  });

  test("throws a UI-safe message on network failure", async () => {
    const { fetch } = mockFetch(new TypeError("Failed to fetch"));
    expect(login("alice", "hunter22", fetch)).rejects.toThrow(
      /could not reach the server/i,
    );
  });

  test("throws on an unexpected success body", async () => {
    const { fetch } = mockFetch(jsonResponse(200, { nope: true }));
    expect(login("alice", "hunter22", fetch)).rejects.toThrow(
      /unexpected response/i,
    );
  });
});

describe("register", () => {
  test("returns the user on 201", async () => {
    const { fetch, calls } = mockFetch(jsonResponse(201, { user: USER }));
    expect(await register("alice", "hunter22", fetch)).toEqual(USER);
    expect(calls[0]?.input).toBe("api/auth/register");
  });

  test("surfaces {error} on 409 (username taken)", async () => {
    const { fetch } = mockFetch(jsonResponse(409, { error: "username taken" }));
    expect(register("alice", "hunter22", fetch)).rejects.toThrow(
      "username taken",
    );
  });

  test("surfaces {error} on 400 (server-side validation)", async () => {
    const { fetch } = mockFetch(jsonResponse(400, { error: "invalid input" }));
    expect(register("a", "short", fetch)).rejects.toThrow("invalid input");
  });

  test("falls back to a generic message when the error body is not JSON", async () => {
    const { fetch } = mockFetch(new Response("boom", { status: 500 }));
    expect(register("alice", "hunter22", fetch)).rejects.toThrow(
      "Request failed (500).",
    );
  });
});

describe("logout", () => {
  test("POSTs to /api/auth/logout with credentials", async () => {
    const { fetch, calls } = mockFetch(new Response(null, { status: 204 }));
    await logout(fetch);
    expect(calls[0]?.input).toBe("api/auth/logout");
    expect(calls[0]?.init?.method).toBe("POST");
    expect(calls[0]?.init?.credentials).toBe("same-origin");
  });

  test("resolves even when the server is unreachable", async () => {
    const { fetch } = mockFetch(new TypeError("Failed to fetch"));
    await logout(fetch); // must not throw — local state is cleared regardless
  });
});